The present invention relates to a process for preparing an amine which is useful as an intermediate for synthesis of medicines, agrochemicals, etc.
The processes for preparing an amine by decarboxylating an α-amino acid have been studied from of old, but there are many methods which have problems not desirable for industrial application such as requiring for drastic heating for long term, or catalyst such as a dangerous peroxide.
Recently the methods which solve the above problems and may be useful for the industrial method have been reported.
For example, (1) the amine is prepared by decarboxylating an α-amino acid under heating in the presence of a vinyl ketone as catalyst in a solvent such as cyclohexanol, etc., (Japanese Patent Publication B4-10452), (2) the amine is prepared by decarboxylating an α-amino acid under heating in the presence of a monoaryl ketone as catalyst in a solvent such as cyclohexanol, etc., (Japanese Patent Publication A 5-255204), (3) the amine is prepared by decarboxylating cis-3-hydroxy-L-proline or trans-3-hydroxy-L-proline in the absence of catalyst in a solvent such as cyclohexanol, etc., (WO97/43256), and (4) the amine is prepared by heating an α-amino acid and an aliphatic saturated ketone followed by hydrogenation (Japanese Patent Publication 2001-220372).